The right fielder launched a solo homer to open the second inning and followed that up with a two-run blast an inning later. Batting in the fifth, the 18-year-old cleared the bases with a double and finished off his night with a sacrifice fly in the sixth.

"He had a really good night, he cleared the fence a few times, and he's swinging the bat really well the last two days," Mariners manager Rob Mummau said. "In batting practice, he uses the whole field and, once it comes game time, he sees the ball and hits the ball. He got the ball middle in and he can drive the ball."

Pimentel, signed by the Mariners as a free agent on July 2, 2009, had never homered twice as a pro. MLB.com's No. 3 Mariners prospect had previously plated four runs in a game three times, most recently on back-to-back days (June 23-24) against Danville and Princeton respectively.

Pimentel, who went yard Monday, is off to a fast start in the Appalachian League, batting .377 with six homers and 19 RBIs. He stands second in the league in the latter two totals. Mummau praised his outfielder, but thinks Pimentel still has a lot of work to do before taking the next step.

"I think if he keeps on having seven-RBI nights that would be real good," Mummau said with a laugh. "I think just trying not to get too complicated and get pitches he can drive. With him, it's about staying in on his front shoulder and trusting his hands and not thinking too much.

"The biggest thing is being more selective at the plate. He has a tendency to chase pitches, so he needs to be more selective. Once he learns to do that, the sky's the limit. Once he learns what kind of hitter he is, he'll be an extremely good hitter."

The 6-foot-1 Dominican has already matched his 2010 home run total, when he clubbed six for the Arizona League Mariners. Overall, he batted .250 with 31 RBIs in 51 games last season. Mummau said he's not shocked by Pimentel's power.

"This is the first year I've seen him. If you watch him take batting practice, it can be impressive to see how far can he hit the ball," he said. "It's not surprising, he's a strong kid."

Daniel Paolini homered and scored twice, while Bryan Brito was 3-for-4 with a triple and two RBIs.

Jose Valdivia improved to 2-0 after allowing a run on five hits and fanning seven over six innings.

Kyle Robinson, a 28th-rounder by the White Sox, hit a solo homer in the loss for the Sox.

This story was not subject to the approval of the National Association of Professional Baseball Leagues or its clubs.